Akiko Shimauchi

University of Chicago, Chicago, Illinois, United States

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Publications (44)84.74 Total impact

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    ABSTRACT: Objective: To evaluate and compare the use of a newly introduced interpretation model for breast nonmass enhancement (NME, defined as an area of enhancement without a three-dimensional, space-occupying lesion) with the use of the standard interpretation method based on BI-RADS. Materials and methods: Two expert and two less-experienced breast imaging radiologists performed reading sessions of 86 malignant and 64 benign NME lesions twice. First, radiologists characterized NME using BI-RADS descriptors and assessed the likelihood of malignancy and need for a biopsy. Second, the likelihood of malignancy and need for a biopsy were assessed with the use of the model, in which three-step characterization of morphological features were performed: (1) selection of distribution modifiers, (2) homogeneous vs. heterogeneous internal enhancement (IE) pattern, and (3) evaluation of presence of "clumped", "clustered ring enhancement (CRE)", and "branching" IE signs. Multireader-multicase receiver operating characteristic analysis was used to evaluate observers' performances. Univariate and multivariate logistic regression analyses were performed for morphology descriptors. Results: With use of the model, average Az of less-experienced radiologists (0.77-0.83; p =0.013) and average sensitivity of all radiologists (96.2-98.2%; p = 0.007) improved significantly. NPV also improved but nonsignificantly (81.1-91.9%; p = 0.055). Multivariate analyses of the second reading showed branching, clumped, and CRE signs to be significant predictors of malignancy in the results of 3, 2, and 2 readers, respectively. Conclusion: The three-step interpretation model for NME has the potential to improve less-experienced radiologists' performances, making them comparable to expert breast imagers.
    No preview · Article · Dec 2015 · European Journal of Radiology
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    ABSTRACT: To evaluate whether visual assessment of T2-weighted imaging (T2WI) or an apparent diffusion coefficient (ADC) could predict lymphovascular invasion (LVI) status in cases with clinically node-negative invasive breast cancer. One hundred and thirty-six patients with 136 lesions underwent MRI. Visual assessment of T2WI, tumour-ADC, peritumoral maximum-ADC and the peritumour-tumour ADC ratio (the ratio between them) were compared with LVI status of surgical specimens. No significant relationship was found between LVI and T2WI. Tumour-ADC was significantly lower in the LVI-positive (n = 77, 896 ± 148 × 10(-6) mm(2)/s) than the LVI-negative group (n = 59, 1002 ± 163 × 10(-6) mm(2)/s; p < 0.0001). Peritumoral maximum-ADC was significantly higher in the LVI-positive (1805 ± 355 × 10(-6) mm(2)/s) than the LVI-negative group (1625 ± 346 × 10(-6) mm(2)/s; p = 0.0003). Peritumour-tumour ADC ratio was significantly higher in the LVI-positive (2.05 ± 0.46) than the LVI-negative group (1.65 ± 0.40; p < 0.0001). Receiver operating characteristic curve analysis revealed that the area under the curve (AUC) of the peritumour-tumour ADC ratio was the highest (0.81). The most effective threshold for the peritumour-tumour ADC ratio was 1.84, and the sensitivity, specificity, positive predictive value and negative predictive value were 77 % (59/77), 76 % (45/59), 81 % (59/73) and 71 % (45/63), respectively. We suggest that the peritumour-tumour ADC ratio can assist in predicting LVI status on preoperative imaging. • Tumour ADC was significantly lower in LVI-positive than LVI-negative breast cancer. • Peritumoral maximum-ADC was significantly higher in LVI-positive than LVI-negative breast cancer. • Peritumour-tumour ADC ratio was significantly higher in LVI-positive breast cancer. • Diagnostic performance of the peritumour-tumour ADC ratio was highest for positive LVI. • Peritumour-tumour ADC ratio showed higher diagnostic ability in postmenopausal than premenopausal patients.
    Full-text · Article · May 2015 · European Radiology
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    ABSTRACT: Purpose To compare positive predictive values (PPVs) of linearly distributed nonmass enhancement (NME) with linear and branching patterns and to identify imaging characteristics of NME that would enable classification as Breast Imaging Reporting and Data System category 3 lesions. Materials and Methods The institutional review board approved this retrospective study and waived the requirement to obtain informed consent. Reports of breast magnetic resonance (MR) examinations (n = 9453) that described NME were reviewed from examinations performed at the study institution from January 2008 to December 2011. NME with linear distribution was allocated to one of two subtypes: linear pattern (arrayed in a line) or branching pattern (with branches). The χ(2) test, Fisher exact test, or Student t test was performed for univariate analyses. Factors that showed a significant association with outcome at univariate analyses were assessed with multivariate analyses by using a logistic regression model. Interobserver agreement of the two subtypes between initial interpretation and the interpretation by two additional radiologists who were blinded to any clinical or pathologic information was evaluated with κ analysis. Results Within the 156 linearly distributed NME lesions, the PPV of the branching pattern (71 of 95 lesions [75%]; 95% confidence interval [CI]: 66%, 84%) was significantly higher than that of the linear pattern (five of 61 lesions [8%]; 95% CI: 1%, 15%) (P < .0001). The PPV of linear pattern lesions smaller than 1 cm was 0% (0 of 30 lesions; 95% CI: 0%, 0%). At multivariate analysis, branching pattern and NME lesion size of 1 cm or greater were significant predictors of malignancy (P < .0001 [odds ratio: 21.6; 95% CI: 7.5, 62.2] and P = .015 [odds ratio: 5.8; 95% CI: 1.4, 24.0], respectively). Substantial interobserver agreement was obtained for differentiating the two subtypes, with κ values of 0.64 (95% CI: 0.51, 0.76), 0.70 (95% CI: 0.59, 0.82), and 0.64 (95% CI: 0.51, 0.76) between the initial interpreter and reviewer 1, the initial interpreter and reviewer 2, and reviewer 1 and reviewer 2, respectively. Conclusion The branching pattern was a significantly stronger predictor of malignancy than was the linear pattern. NME lesions with a linear pattern that are smaller than 1 cm can be managed with follow-up. (©) RSNA, 2015.
    No preview · Article · Apr 2015 · Radiology
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    ABSTRACT: The primary modality for breast cancer screening is mammography. Recent investigations, however, have indicated that an insufficient number of life-threatening cases have been detected by mammography while mammography can often results in a large number of overdiagnoses. To make breast cancer screening more effective, potential factors that influence screening efficacy need to be elucidated. Breast density is one of limiting factors for breast cancer detection using mammography. In this article, influence of breast density on breast screening is explained. Current topics related to breast density, objective assessment of breast density using applications, revision of breast composition classification in Breast Imaging-Reporting and Data System Mammography fifth edition, and legislative movement regarding breast density in the United States, are also mentioned in this review article.
    No preview · Article · Mar 2015 · Breast Cancer
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    ABSTRACT: To compare DCE-MRI parameters from scans of breast lesions at 1.5 Tesla and 3 Tesla. Eleven patients underwent paired MRI examinations on both Philips 1.5T and 3T systems using a standard clinical fat-suppressed, T1-weighted DCE-MRI protocol, with 70-76 s temporal resolution. Signal intensity-versus-time curves were fit with an empirical mathematical model to obtain semi-quantitative measures of uptake and washout rates as well as time-to-peak enhancement (TTP). Maximum percent enhancement and signal enhancement ratio (SER) were also measured for each lesion. Percent differences between parameters measured at the two field strengths were compared. TTP and SER parameters measured at 1.5T and 3T were similar; with mean absolute differences of 19% and 22% respectively. Maximum percent signal enhancement was significantly higher at 3T than at 1.5T (p=0.006). Qualitative assessment showed that image quality was significantly higher at 3T (p=0.005). Our results suggest that TTP and SER are more robust to field strength change than other measured kinetic parameters and therefore measurements of these parameters can be more easily standardized than measurements of other parameters derived from DCE-MRI. Semi-quantitative measures of overall kinetic curve shape showed higher reproducibility than discrete classification of kinetic curve early and delayed phases in a majority of the cases studied. Advances in knowledge: Qualitative measures of curve shape are not consistent across field strength even when acquisition parameters are standardized. Quantitative measures of overall kinetic curve shape, in contrast, have higher reproducibility.
    Full-text · Article · Mar 2015 · The British journal of radiology
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    ABSTRACT: To quantify kinetic heterogeneity of breast masses that were initially detected with dynamic contrast-enhanced MRI, using whole-lesion kinetic distribution data obtained from computer-aided evaluation (CAE), and to compare that with standard kinetic curve analysis. Clinical MR images from 2006 to 2011 with breast masses initially detected with MRI were evaluated with CAE. The relative frequencies of six kinetic patterns (medium-persistent, medium-plateau, medium-washout, rapid-persistent, rapid-plateau, rapid-washout) within the entire lesion were used to calculate kinetic entropy (KE), a quantitative measure of enhancement pattern heterogeneity. Initial uptake (IU) and signal enhancement ratio (SER) were obtained from the most-suspicious kinetic curve. Mann-Whitney U test and ROC analysis were conducted for differentiation of malignant and benign masses. Forty benign and 37 malignant masses comprised the case set. IU and SER were not significantly different between malignant and benign masses, whereas KE was significantly greater for malignant than benign masses (p = 0.748, p = 0.083, and p < 0.0001, respectively). Areas under ROC curve for IU, SER, and KE were 0.479, 0.615, and 0.662, respectively. Quantification of kinetic heterogeneity of whole-lesion time-curve data with KE has the potential to improve differentiation of malignant from benign breast masses on breast MRI. • Kinetic heterogeneity can be quantified by computer-aided evaluation of breast MRI • Kinetic entropy was greater in malignant masses than benign masses • Kinetic entropy has the potential to improve differentiation of breast masses.
    Full-text · Article · Feb 2015 · European Radiology
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    ABSTRACT: PURPOSE Can aggressive MRI characteristics and receptor profile of invasive breast cancers be used to predict clinical outcome and metastases/recurrence rates? METHOD AND MATERIALS 54 patients (mean age 56 yo) with biopsy-proven invasive breast cancer and staging MRI (1.5T Phillips) at University of Chicago from 2002-2003 were included in a HIPAA-compliant retrospective study. Patients with prior history of invasive or in-situ breast cancer or distant metastases at time of breast cancer diagnosis were excluded. Imaging and clinical notes were reviewed to identify local recurrence or distant metastases. Average follow up time was 7.8 years. All breast cancers were measured on MRI as maximum diameter in axial dimension. Aggressive MRI morphologic features such as non-mass enhancement (NME), rim or heterogeneous enhancement and multifocality were analyzed in consensus by two board-certified fellowship-trained radiologists. Receptor profiles of all cancers were obtained from pathology reports. RESULTS Histology yielded IDC 46/54 (85%) and ILC 8/54 (15%). 9/54 (17%) of the total patients developed distant metastases. Average time to metastases was 2.8 years, range 0.7 to 6.8 yrs. Histology of all metastatic cancers was IDC. 33% of cancers were grade 2 and 37% were grade 3. Grade 3 tumors metastasized in (6/20) 30% of cases and grade 2 in (1/18) 6%; tumor grade was not included in the pathology report in 2 cases. Cancers were categorized based on receptor profile as triple negative (9/54; 17%), Her2+ (12/54; 22%), and ER+Her2- (33/54; 61%). ER+ Her2- cancers metastasized in 9% (3/33) and all were unifocal. Her+ cancers metastasized in 25% (3/12) (1 unifocal, 2 multifocal) and triple negative cancers in 33% (3/9) (1 unifocal, 2 multifocal). Analysis of the MRI morphologic features showed that 25% of rim-enhancing tumors, 22% with NME, 18% of multifocal and 16% of unifocal cancers metastasized. CONCLUSION Pilot data shows that grade 3, triple negative, NME and multifocal IDC have higher rates of metastases compared to unifocal, low grade, and ILC. Distant metastases presented as late as 6.8 yrs after diagnosis. We intend to analyze a total of 200 patients in our final study. CLINICAL RELEVANCE/APPLICATION To determine the group of patients that can benefit from close follow up and metastatic work up to prevent or detect local recurrence/distant metastases.
    No preview · Conference Paper · Dec 2013
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    ABSTRACT: PURPOSE/AIM To review the influence of receptor profile and residual cellularity on MRI findings in breast cancer patients undergoing neoadjuvant chemotherapy (NAC). To better identify patients showing residual invasive cancer post-NAC despite no or minimal enhancement on MRI and to understand factors influencing this rad-path discrepancy. To better delineate extent of residual disease and determine appropriate surgical treatment post NAC. CONTENT ORGANIZATION 10 cases of breast cancer will be shown with pre- and post-NAC MRI and histopathologic images. Differences in imaging response associated with different receptor profiles and patterns of pathologic response to therapy will be reviewed. Pathologic staging of post-NAC breast cancers will be discussed. SUMMARY Major teaching points: Some breast cancers become less cellular post NAC without significantly decreasing in size. These cancers may have no or minimal contrast enhancement on MRI. Evaluation of non-subtracted contrast and delayed images is of increased importance in order to evaluate the extent of residual tumor. ER+Her2- cancers more often have subtle imaging findings after treatment as compared to triple negative and Her2+ cancers. Evaluation of different tumor morphologies and patterns of response to NAC can be helpful in surgical planning.
    No preview · Conference Paper · Dec 2013
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    ABSTRACT: PURPOSE To investigate the change of breast parenchymal enhancement (BPE) on MRI, in the contralateral normal breast of patients who received neoadjuvant chemotherapy (NAC) for breast cancer. METHOD AND MATERIALS 20 patients with breast cancer (mean age, 57 years; age range, 35-87 years) treated with NAC who had pre-chemo and post-chemo (pre-surgery) MRI between Jan 2010 and Jan 2012 were reviewed retrospectively. BPE of the contralateral normal breast was analyzed using Dynacad. Regions of interest (ROIs) were traced manually on pre and 5 dynamic T1WI post contrast series , at the same 4 locations of the normal breast on pre-NAC and post-NAC scans. Average relative increase in intensity (%) compared to the intensity on precontrast images within the ROIs was obtained at each of the 5 post contrast time points, and the values from the 4 ROIs were averaged to give a single mean relative signal increase per scan. The effect of NAC on the change of BPE was evaluated using the student t test. Change in categorical scales (minimal, mild, moderate or marked) to rate BPE by radiologists was also evaluated, using the Chi-square test. Subgroup analysis based on menopausal status (premenopausal (n=8), postmenopausal (n=12)) was performed. RESULTS The average relative signal increase at the 5 time points were 15.2, 31.1, 39.7, 46.2 and 50.5% on pre-NAC scans, and 5.7, 14.9, 20.1, 23.4 and 26.2% on post-NAC scans. Statistically significant differences were found at all time points (p=0.013, 0.002, 0.001, <0.001, <0.001 at each time point respectively). The numbers of cases categorized into minimal, mild, moderate, and marked BPE were 4, 10, 6, and 0 on pre-NAC scans, and 17, 3, 0, and 0 cases respectively on post-NAC scans, with a statistically significant difference (p<0.001) in the distribution. In both premenopausal and post menopausal subgroups, a statistically significant decrease in average relative signal increase was found at the 2nd through 5th time points. CONCLUSION BPE in the contralateral normal breast showed a statistically significant decrease after NAC compared to pre-NAC scans, both in early and delayed postcontrast images. The significant decrease was seen regardless of menopausal status. CLINICAL RELEVANCE/APPLICATION Evaluation of functional changes in breast tissue due to NAC may improve the understanding of the influence of NAC on hormonal levels and hemodynamics in pre and post menopausal breast cancer patients
    No preview · Conference Paper · Dec 2013
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    ABSTRACT: To compare magnetic resonance imaging (MRI) and ultrasound (US) for axillary lymph node (LN) staging in breast cancer patients in an observer-performance study. An observer-performance study was conducted with five breast radiologists reviewing 50 consecutive patients of newly diagnosed invasive breast cancer with the use of ipsilateral axillary MRI and US. LN status was pathologically proved in all patients. Each observer reviewed the images in two separate sessions: one for MRI and the other for US. Observers were asked to indicate their confidence of the presence of at least one ipsilateral metastatic LN on a quasi-continuous rating scale and whether they recommend percutaneous biopsy preoperatively. Receiver operating characteristic (ROC) analysis and area under the ROC curve were used to characterize diagnostic performance. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated from whether observers recommended biopsy. There were no statistically significant differences in each observer's performance between MRI and US, or in the performance of all observers as a group, in terms of ROC analysis. There were no statistically significant differences in sensitivity, specificity, PPV, or NPV between MRI and US, but there were statistically significant improvements in specificity and PPV from either MRI or US alone to MRI and US combined. Observer performance on MRI and US are comparable for axillary LN staging. When US and MRI are concordant for positive findings, higher specificity and PPV can be obtained.
    Full-text · Article · Nov 2013 · Academic radiology
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    ABSTRACT: Inhomogeneously broadened, non-Lorentzian water resonances have been observed in small image voxels of breast tissue. The non-Lorentzian components of the water resonance are probably produced by bulk magnetic susceptibility shifts caused by dense, deoxygenated tumor blood vessels (the 'blood oxygenation level-dependent' effect), but can also be produced by other characteristics of local anatomy and physiology, including calcifications and interfaces between different types of tissue. Here, we tested the hypothesis that the detection of non-Lorentzian components of the water resonance with high spectral and spatial resolution (HiSS) MRI allows the classification of breast lesions without the need to inject contrast agent. Eighteen malignant lesions and nine benign lesions were imaged with HiSS MRI at 1.5 T. A new algorithm was developed to detect non-Lorentzian (or off-peak) components of the water resonance. After a Lorentzian fit had been subtracted from the data, the largest peak in the residual spectrum in each voxel was identified as the major off-peak component of the water resonance. The difference in frequency between these off-peak components and the main water peaks, and their amplitudes, were measured in malignant lesions, benign lesions and breast fibroglandular tissue. Off-peak component frequencies were significantly different between malignant and benign lesions (p < 0.001). Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of HiSS off-peak component analysis compared with dynamic contrast-enhanced (DCE) MRI parameters. The areas under the ROC curves for the 'DCE rapid uptake fraction', 'DCE washout fraction', 'off-peak component amplitude' and 'off-peak component frequency' were 0.75, 0.83, 0.50 and 0.86, respectively. These results suggest that water resonance lineshape analysis performs well in the classification of breast lesions without contrast injection and could improve the diagnostic accuracy of clinical breast MR examinations. In addition, this approach may provide an alternative to DCE MRI in women who are at risk for adverse reactions to contrast media. Copyright © 2012 John Wiley & Sons, Ltd.
    No preview · Article · May 2013 · NMR in Biomedicine
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    ABSTRACT: The purpose of this research is to evaluate the potential for identifying malignant breast lesions and their margins on large specimen MRI, in comparison to specimen radiography and clinical dynamic contrast enhanced MRI (DCE-MRI). Breast specimens were imaged with an MR scanner immediately after surgery, with an IRB-approved protocol and with the patients' informed consent. Specimen sizes were at least 5 cm in diameter and approximately 1 to 4 cm thick. Coronal and axial gradient echo MR images without fat suppression were acquired over the whole specimens using a 9.4T animal scanner. Findings on specimen MRI were compared with findings on specimen radiograph, and their volumes were compared with measurements obtained from clinical DCE-MRI. The results showed that invasive ductal carcinoma (IDC) lesions were easily identified using MRI and the margins were clearly distinguishable from nearby tissue. However, ductal carcinoma in situ (DCIS) lesions were not clearly discernible and were diffused with poorly defined margins on MRI. Calcifications associated with DCIS were visualized in all specimens on specimen radiograph. There is a strong correlation between the maximum diameter of lesions as measured by radiograph and MRI (r = 0.93), as well as the maximum diameter measured by pathology and radiograph/MRI (r>0.75). The volumes of IDC measured on specimen MRI were slightly smaller than those measured on DCE-MRI. Imaging of excised human breast lumpectomy specimens with high magnetic field MRI provides promising results for improvements in lesion identification and margin localization for IDC. However, there are technical challenges in visualization of DCIS lesions. Improvements in specimen imaging are important, as they will provide additional information to standard radiographic analysis.
    Full-text · Article · Nov 2012 · Journal of Applied Clinical Medical Physics
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    ABSTRACT: PURPOSE To evaluate the visibility of breast tumors on large specimen MRI, in comparison to specimen radiography and clinical dynamic contrast enhanced MRI (DCE-MRI). METHOD AND MATERIALS Breast specimens (n=15) were imaged with a MR scanner immediately after surgery, with an IRB approved protocol and with the patient’s informed consent. Specimen sizes were at least 5 cm in diameter and about 1 to 4 cm thick. Coronal and axial gradient echo MRI with and/or without fat suppression were acquired over the whole specimen using a 9.4T animal scanner with 72 mm birdcage volume coil. The lesions detected on MRI were compared with specimen radiograph and their volumes were compared with measurements obtained from clinical DCE-MRI. RESULTS Invasive ductal carcinoma (IDC) lesions were easily identified using MRI and the margins were clearly distinguishable from adjacent tissue. However, ductal carcinoma in situ (DCIS) lesions were not clearly discernible and were diffused with poorly defined margins on MRI. All calcifications associated with DCIS were visualized on specimen radiograph. The calcifications are only visible on MRI when the DCIS component is surrounded by an IDC lesion. The volumes of IDC measured on specimen MRI were not significantly different from those measured on DCE-MRI. CONCLUSION Imaging of excised human breast lumpectomy specimens with high magnetic field MRI provides promising results for improvements in lesion identification and margin localization for IDC. However, there is a technical challenge in visualization of DCIS lesions. Further improvement is necessary in visualization of DCIS lesions in order to aid pathologists in routine assessment of specimens, thus contributing to better treatment of breast cancer patients. CLINICAL RELEVANCE/APPLICATION High magnetic field specimen MRI provides better visualization of IDC lesions than radiography. Protocols and techniques developed in this study could be used to aid pathologists in routine analysis.
    No preview · Conference Paper · Dec 2011
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    ABSTRACT: PURPOSE For lymph node staging in breast cancer patients, ultrasound (US) and MRI are commonly used. The purpose of this study is to compare these two imaging modalities in accuracy of axillary lymph node (LN) staging for breast cancer patients. METHOD AND MATERIALS Observer performance test was conducted by dedicated breast radiologists. Consecutive 50 patients with newly diagnosed invasive breast cancer who underwent staging MRI, ipsilateral axillary US in 2009 were used. LN status of all patients were pathologically proven by surgery (sentinel LN biopsy and/or axillary lymph node dissection). MR images for the observers consisted of axial and sagittal T2 weighted images and axial post contrast T1 weighted images (slice thickness was 1 mm and in-plane resolution was 0.8 mm for all images) and US images consisted of all available static US images of the ipsileteral axilla. No information about primary cancers were provided. Confidence rating for presence of at least one positive lymph node in ipsilateral axilla was made using continuous rating scale. Observers were also asked to indicate if percutaneous biopsy was recommended preoperatively. These results were compared with final pathology results. The Az values, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for each modality were obtained. RESULTS Our preliminary results are followings. Average sensitivity and specificity were 58% and 80% for US and 69% and 74% for MRI. PPV and NPV were 59% and 80 % for US and 56% and 83% for MRI. When US and MRI findings were concordant, PPV was 76% and NPV was 80%. Average Az values of MR and US are comparable and there was no significant difference between them. Sensitivity of MR is significantly higher than that of US, and no significant difference in specificity, PPV and NPV between US and MR. CONCLUSION Observers’ performance with MR and US are comparable in detecting metastatic lymph node in Az value, however; when they were forced to make an alternative decision, MR was more sensitive. CLINICAL RELEVANCE/APPLICATION MRI and US are comparable for staging lymph node in breast cancer patient.
    No preview · Conference Paper · Nov 2011
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    ABSTRACT: The aims of this study were to evaluate high spectral and spatial resolution (HiSS) magnetic resonance imaging (MRI) for the diagnosis of breast cancer without the injection of contrast media by comparing the performance of precontrast HiSS images to that of conventional contrast-enhanced, fat-suppressed, T1-weighted images on the basis of image quality and in the task of classifying benign and malignant breast lesions. Ten benign and 44 malignant lesions were imaged at 1.5 T with HiSS (precontrast administration) and conventional fat-suppressed imaging (3-10 minutes after contrast administration). This set of 108 images, after randomization, was evaluated by three experienced radiologists blinded to the imaging technique. Breast Imaging Reporting and Data System morphologic criteria (lesion shape, lesion margin, and internal signal intensity pattern) and final assessment were used to measure reader performance. Image quality was evaluated on the basis of boundary delineation and quality of fat suppression. An overall probability of malignancy was assigned to each lesion for HiSS and conventional images separately. On boundary delineation and quality of fat suppression, precontrast HiSS scored similarly to conventional postcontrast MRI. On benign versus malignant lesion separation, there was no statistically significant difference in receiver-operating characteristic performance between HiSS and conventional MRI, and HiSS met a reasonable noninferiority condition. Precontrast HiSS imaging is a promising approach for showing lesion morphology without blooming and other artifacts caused by contrast agents. HiSS images could be used to guide subsequent dynamic contrast-enhanced MRI scans to maximize spatial and temporal resolution in suspicious regions. HiSS MRI without contrast agent injection may be particularly important for patients at risk for contrast-induced nephrogenic systemic fibrosis or allergic reactions.
    Full-text · Article · Sep 2011 · Academic radiology
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    ABSTRACT: A multiparametric computer-aided diagnosis scheme that combines information from T1-weighted dynamic contrast-enhanced (DCE)-MRI and T2-weighted MRI was investigated using a database of 110 malignant and 86 benign breast lesions. Automatic lesion segmentation was performed, and three categories of lesion features (geometric, T1-weighted DCE, and T2-weighted) were automatically extracted. Stepwise feature selection was performed considering only geometric features, only T1-weighted DCE features, only T2-weighted features, and all features. Features were merged with Bayesian artificial neural networks, and diagnostic performance was evaluated by ROC analysis. With leave-one-lesion-out cross-validation, an area under the ROC curve value of 0.77±0.03 was achieved with T2-weighted-only features, indicating high diagnostic value of information in T2-weighted images. Area under the ROC curve values of 0.79±0.03 and 0.80 ± 0.03 were obtained for geometric-only features and T1-weighted DCE-only features, respectively. When all features were considered, an area under the ROC curve value of 0.85±0.03 was achieved. We observed P values of 0.006, 0.023, and 0.0014 between the geometric-only, T1-weighted DCE-only, and T2-weighted-only features and all features conditions, respectively. When ranked, the P values satisfied the Holm-Bonferroni multiple-comparison test; thus, the improvement of multiparametric computer-aided diagnosis was statistically significant. A computer-aided diagnosis scheme that combines information from T1-weighted DCE and T2-weighted MRI may be advantageous over conventional T1-weighted DCE-MRI computer-aided diagnosis.
    No preview · Article · Aug 2011 · Magnetic Resonance in Medicine
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    ABSTRACT: To compare the pathology and kinetic characteristics of breast lesions with focus-, mass-, and nonmass-like enhancement. A total of 852 MRI detected breast lesions in 697 patients were selected for an IRB approved review. Patients underwent dynamic contrast enhanced MRI using one pre- and three to six postcontrast T(1)-weighted images. The "type" of enhancement was classified as mass, nonmass, or focus, and kinetic curves quantified by the initial enhancement percentage (E(1)), time to peak enhancement (T(peak)), and signal enhancement ratio (SER). These kinetic parameters were compared between malignant and benign lesions within each morphologic type. A total of 552 lesions were classified as mass (396 malignant, 156 benign), 261 as nonmass (212 malignant, 49 benign), and 39 as focus (9 malignant, 30 benign). The most common pathology of malignant/benign lesions by morphology: for mass, invasive ductal carcinoma/fibroadenoma; for nonmass, ductal carcinoma in situ (DCIS)/fibrocystic change(FCC); for focus, DCIS/FCC. Benign mass lesions exhibited significantly lower E(1), longer T(peak), and lower SER compared with malignant mass lesions (P < 0.0001). Benign nonmass lesions exhibited only a lower SER compared with malignant nonmass lesions (P < 0.01). By considering the diverse pathology and kinetic characteristics of different lesion morphologies, diagnostic accuracy may be improved.
    Preview · Article · Jun 2011 · Journal of Magnetic Resonance Imaging
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    ABSTRACT: To evaluate a computer-aided diagnosis (CADx) system for dynamic contrast material-enhanced magnetic resonance (MR) imaging and compare it with a currently used clinical method of interpreting breast MR image findings that includes the use of commercially available automated software for kinetic image data processing and visualization. In this HIPAA-compliant, institutional review board-approved study, a training set of 121 breast lesions (77 malignant, 44 benign) was used to train the CADx system. After practicing with 10 training cases, six breast imaging radiologists assessed the likelihood of malignancy and the need for biopsy with a separate test set of 60 lesions (30 malignant, 30 benign). Their performances in differentiating between benign and malignant breast lesions both without (conventional lesion viewing, output from commercially available breast MR imaging analysis software) and with the aid of the CADx workstation (with classification yielding an estimation of the probability of malignancy for each lesion) were evaluated with receiver operating characteristic analysis. When CADx was used, the average performance of the radiologists was significantly improved, as indicated by increases in mean area under the receiver operating characteristic curve (from 0.80 to 0.84, P = .007), mean sensitivity (from 83% to 88%, P = .001), and average number of biopsy recommendations for malignant cases (1.7 more biopsies for malignant lesions with use of CADx, P = .032). Although the mean specificity improved (from 50% to 53%), the improvement was not significant (P = .2). Use of the CADx system improved the radiologists' performance in differentiating between malignant and benign MR imaging-depicted breast lesions.
    No preview · Article · Mar 2011 · Radiology
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    ABSTRACT: Improvements in the reliable diagnosis of preinvasive ductal carcinoma in situ (DCIS) by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are needed. In this study, we present a new characterization of early contrast kinetics of DCIS using high temporal resolution (HiT) DCE-MRI and compare it with other breast lesions and normal parenchyma. Forty patients with mammographic calcifications suspicious for DCIS were selected for HiT imaging using T(1)-weighted DCE-MRI with ∼7 s temporal resolution for 90 s post-contrast injection. Pixel-based and whole-lesion kinetic curves were fit to an empirical mathematical model (EMM) and several secondary kinetic parameters derived. Using the EMM parameterized and fitted concentration time curve for subsequent analysis allowed for calculation of kinetic parameters that were less susceptible to fluctuations due to noise. The parameters' initial area under the curve (iAUC) and contrast concentration at 1 min (C(1 min)) provided the highest diagnostic accuracy in the task of distinguishing pathologically proven DCIS from normal tissue. There was a trend for DCIS lesions with solid architectural pattern to exhibit a negative slope at 1 min (i.e. increased washout rate) compared to those with a cribriform pattern (p < 0.04). This pilot study demonstrates the feasibility of quantitative analysis of early contrast kinetics at high temporal resolution and points to the potential for such an analysis to improve the characterization of DCIS.
    No preview · Article · Oct 2010 · Physics in Medicine and Biology
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    ABSTRACT: To develop and evaluate a computerized segmentation method for breast MRI (BMRI) mass-lesions. A computerized segmentation algorithm was developed to segment mass-like-lesions on breast MRI. The segmentation algorithm involved: (i) interactive lesion selection, (ii) automatic intensity threshold estimation, (iii) connected component analysis, and (iv) a postprocessing procedure for hole-filling and leakage removal. Seven observers manually traced the borders of all slices of 30 mass-lesions using the same tools. To initiate the computerized segmentation, each user selected a seed-point for each lesion interactively using two methods: direct seed-point and robust region of interest (ROI) selections. The manual and computerized segmentations were compared pair-wise using the measured size and overlap to evaluate similarity, and the reproducibility of the computerized segmentation was compared with the interobserver variability of the manual delineations. The observed inter- and intraobserver variations were similar (P > 0.05). Computerized segmentation using the robust ROI selection method was significantly (P < 0.001) more reproducible in measuring lesion size (stDev 1.8%) than either manual contouring (11.7%) or computerized segmentation using directly placed seed-point method (13.7%). The computerized segmentation method using robust ROI selection is more reproducible than manual delineation in terms of measuring the size of a mass-lesion.
    No preview · Article · Jul 2010 · Journal of Magnetic Resonance Imaging